TWO DIFFERENT CONDUCTIVE BUMP STOPS ON CMOS-MEMS BONDED STRUCTURE
Provided herein is a method including forming a micro-electro-mechanical system (“MEMS”) wafer including a first MEMS device and a second MEMS device. A complementary metal-oxide semiconductor (“CMOS”) wafer is formed including a first electrically conductive via and a second electrically conductive via. A layer stack including a first conductive layer, a second conductive layer, and a bond layer is deposited over the first electrically conductive via and the second electrically conductive via. The layer stack is etched to define a first standoff, a second standoff, a third standoff, a first bump stop over the first electrically conductive via, and a second bump stop over the second electrically conductive via. The first bump stop and the second bump stop are etched to remove the bond layer. The first bump stop is further etched to remove the second conductive layer. The MEMS wafer is bonded to the CMOS wafer.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/361,441 filed Jul. 12, 2016, entitled “METHOD OF FABRICATING TWO DIFFERENT CONDUCTIVE BUMP S TOP ON CMOS-MEMS BONDING STRUCTURE”.
BACKGROUNDMEMS (“micro-electro-mechanical systems”) are a class of devices that are fabricated using semiconductor-like processes and exhibit mechanical characteristics. For example, MEMS devices may include the ability to move or deform. In many cases, but not always, MEMS interact with electrical signals. A MEMS device may refer to a semiconductor device that is implemented as a micro-electro-mechanical system. A MEMS device includes mechanical elements and may optionally include electronics (e.g. electronics for sensing). MEMS devices include but are not limited to, for example, gyroscopes, accelerometers, magnetometers, pressure sensors, etc. During fabrication, it may be desirable to create various different MEMS devices on the same wafer.
SUMMARYProvided herein is a method including forming MEMS wafer including a first MEMS device and a second MEMS device. A CMOS wafer is formed including a first electrically conductive via and a second electrically conductive via. A layer stack including a first conductive layer, a second conductive layer, and a bond layer is deposited over the first electrically conductive via and the second electrically conductive via. The layer stack is etched to define a first standoff, a second standoff, a third standoff, a first bump stop over the first electrically conductive via, and a second bump stop over the second electrically conductive via. The first bump stop and the second bump stop are etched to remove the bond layer. The first bump stop is further etched to remove the second conductive layer. The MEMS wafer is bonded to the CMOS wafer. These and other features and advantages will be apparent from a reading of the following detailed description.
Before various embodiments are described in greater detail, it should be understood that the embodiments are not limiting, as elements in such embodiments may vary. It should likewise be understood that a particular embodiment described and/or illustrated herein has elements which may be readily separated from the particular embodiment and optionally combined with any of several other embodiments or substituted for elements in any of several other embodiments described herein.
It should also be understood that the terminology used herein is for the purpose of describing the certain concepts, and the terminology is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood in the art to which the embodiments pertain.
Unless indicated otherwise, ordinal numbers (e.g., first, second, third, etc.) are used to distinguish or identify different elements or steps in a group of elements or steps, and do not supply a serial or numerical limitation on the elements or steps of the embodiments thereof. For example, “first,” “second,” and “third” elements or steps need not necessarily appear in that order, and the embodiments thereof need not necessarily be limited to three elements or steps. It should also be understood that, unless indicated otherwise, any labels such as “left,” “right,” “front,” “back,” “top,” “middle,” “bottom,” “beside,” “forward,” “reverse,” “overlying,” “underlying,” “up,” “down,” or other similar terms such as “upper,” “lower,” “above,” “below,” “under,” “between,” “over,” “vertical,” “horizontal,” “proximal,” “distal,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. It should also be understood that the singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
Terms such as “over,” “overlying,” “above,” “under,” etc. are understood to refer to elements that may be in direct contact or may have other elements in-between. For example, two layers may be in overlying contact, wherein one layer is over another layer and the two layers physically contact. In another example, two layers may be separated by one or more layers, wherein a first layer is over a second layer and one or more intermediate layers are between the first and second layers, such that the first and second layers do not physically contact.
A micro-electro-mechanical systems (“MEMS”) device includes mechanical elements and may optionally include electronics (e.g. electronics for sensing). MEMS devices include but are not limited to, for example, gyroscopes, accelerometers, magnetometers, pressure sensors, etc. During fabrication, it may be desirable to create various different MEMS devices on the same wafer. The different MEMS devices may include mechanical elements that work best with different electrodes on a complementary metal-oxide semiconductor (“CMOS”) wafer. For example, a gyroscope MEMS device may optimally operate with a first electrode on a CMOS wafer, and an accelerometer MEMS device my optimally operate with a second electrode on the same CMOS wafer. According to embodiments described herein, the first and second electrodes on the same CMOS wafer include different thickness and/or compositions that are optimized for the corresponding MEMS devices. As such, it is desirable during fabrication to create various different MEMS devices on a MEMS wafer with different corresponding electrodes on the same CMOS wafer.
Referring now to
A layer stack 106 has been deposited over the first electrically conductive vias 102 and the second electrically conductive vias 104. In various embodiments, the layer stack 106 may be deposited by any method, including, but not limited to, physical vapor deposition (“PVD”) and chemical vapor deposition (“CVD”). The layer stack 106 includes a first conductive layer 108, a second conductive layer 110, and a bond layer 112. The second conductive layer 110 overlies the first conductive layer 108, and the bond layer 112 overlies the second conductive layer 110.
The first conductive layer 108 may include any kind of bi-layer materials (e.g. Ti, TiN, etc.), and the second conductive layer 110 may include any kind of bi-layer materials (e.g. Ti, TiN, etc.). In different embodiments, the first conductive layer 108 and the second conductive layer 110 may include the same or different materials. The bond layer 112 may include an electrically conductive material (e.g. aluminum, etc.).
Referring now to
After patterning, the first bump stops 214, the second bump stops 216, the first standoff 218, the second standoff 220, and the third standoff 222 all include portions of the first conductive layer 108, the second conductive layer 110, and the bond layer 112. In addition, after patterning, the first bump stops 214 are over the first electrically conductive vias 102, and the second bump stops 216 are over the second electrically conductive vias 104.
Referring now to
In various embodiments, the first standoff 218, the second standoff 220, and the third standoff 222 are all protected by, for example, a photoresist mask 324. The photoresist mask 324 is deposited over the first standoff 218, the second standoff 220, and the third standoff 222 prior to the selective etching of the first bump stops 214 and the second bump stops 216. In some embodiments, the photoresist mask 324 also protects other areas and components of the CMOS wafer 100. For example, the photoresist mask 324 may protect a outgassing material 326.
Referring now to
In various embodiments, the first standoff 218, the second standoff 220, the third standoff 222, and the second bump stops 216 are all protected by, for example, a photoresist mask 424. The photoresist mask 424 is deposited over the first standoff 218, the second standoff 220, the third standoff 222, and the second bump stops 216 prior to the further selective etching of the first bump stops 214. In some embodiments, the photoresist mask 424 also protects other areas and components of the CMOS wafer 100. For example, the photoresist mask 424 may protect the outgassing material 326. As a result of the further selective etching, the first bump stops 214 include a single layer containing the first conductive layer 108. In addition, the second bump stops 216 include a double layer containing the first conductive layer 108 and the second conductive layer 110.
Referring now to
The eutectic bonding of the CMOS wafer 100 to the MEMS wafer 528 forms a first cavity 532 and a second cavity 534. The first cavity 532 and the second cavity 534 are defined by the CMOS wafer 100 and the MEMS wafer 528. The first cavity 532 surrounds the first MEMS device 536 and the first bump stops 214. The second cavity 534 surrounds the second MEMS device 538 and the second bump stops 216.
The first MEMS device 536 and the second MEMS device 538 may be any MEMS device (e.g. gyroscope, accelerometer, magnetometer, pressure sensor, etc.), and may include the same MEMS devices or different MEMS devices. For example, the first MEMS device 536 may be an accelerometer and the second MEMS device 538 may be a gyroscope. In various embodiments, the first cavity 532 and the second cavity 534 are sealed, for example, by the eutectic bonds. As a result of the sealing, the first MEMS device 536 may include a first gas pressure and the second MEMS device 538 may include a second gas pressure. In various embodiments, the first gas pressure and the second gas pressure may be different or the same, and one or both of the pressures may be a vacuum.
As described above, the first bump stops 214 include a single layer (e.g. the first conductive layer 108) with a first height. In addition, the second bump stops 216 include a double layer (e.g. the first conductive layer 108 and the second conductive layer 110) with a second height that is larger than the first height. Furthermore, the first bump stops 214 and the second bump stops 216 may include any number of layers, and the number of layers may be different or equal. In various embodiments, the first bump stops 214 and the second bump stops 216 may perform any number of similar or different functions. For example, one or more of the first bump stops 214 and the second bump stops 216 may function as sensing electrodes, shield electrodes, etc.
In further embodiments, the first cavity 532 of the first MEMS device 536 may include one or more of the first bump stops 214 as well as one or more of the second bump stops 216. In addition, the second cavity 534 of the second MEMS device 538 may include one or more of the first bump stops 214 as well as one or more of the second bump stops 216. Therefore, it is understood that by using the masking and etching described herein, any combination of first bump stops 214 and second bump stops 216 may be formed within one or more cavities associated with one or more MEMS devices.
Referring now to
A layer stack 606 has been deposited over the first electrically conductive vias 602 and the second electrically conductive vias 604. In various embodiments, the layer stack 606 may be deposited by any method, including, but not limited to, physical vapor deposition (“PVD”) and chemical vapor deposition (“CVD”). The layer stack 606 includes a first conductive layer 608 and a second conductive layer 610. The second conductive layer 610 overlies the first conductive layer 608.
The first conductive layer 608 may include any kind of bi-layer materials (e.g. Ti, TiN, etc.), and the second conductive layer 610 may include any kind of bi-layer materials (e.g. Ti, TiN, etc.). In different embodiments, the first conductive layer 608 and the second conductive layer 610 may include the same or different materials.
Referring now to
Referring now to
Referring now to
After patterning, the first bump stops 914 include portions of the first conductive layer 608 and the bond layer 812. Furthermore, the second bump stops 916, the first standoff 918, the second standoff 920, and the third standoff 922 all include portions of the first conductive layer 108, the second conductive layer 110, and the bond layer 812. In addition, after patterning, the first bump stops 914 are over the first electrically conductive vias 102, and the second bump stops 916 are over the second electrically conductive vias 104. In some embodiments, at least one of the first standoff 918, the second standoff 920, and the third standoff 922 may be made of the first conductive layer 108 and the bond layer 812.
Referring now to
In various embodiments, the first standoff 918, the second standoff 920, and the third standoff 922 are all protected by, for example, a photoresist mask 1024. The photoresist mask 1024 is deposited over the first standoff 918, the second standoff 920, and the third standoff 922 prior to the selective etching of the first bump stops 914 and the second bump stops 916. In some embodiments, the photoresist mask 1024 also protects other areas and components of the CMOS wafer 600. For example, the photoresist mask 1024 may protect a outgassing material 1026.
Referring now to
The eutectic bonding of the CMOS wafer 600 to the MEMS wafer 1128 forms a first cavity 1132 and a second cavity 1134. The first cavity 1132 and the second cavity 1134 are defined by the CMOS wafer 600 and the MEMS wafer 1128. The first cavity 1132 surrounds the first MEMS device 1136 and the first bump stops 914. The second cavity 1134 surrounds the second MEMS device 1138 and the second bump stops 916.
The first MEMS device 1136 and the second MEMS device 1138 may be any MEMS device (e.g. gyroscope, accelerometer, magnetometer, pressure sensor, etc.), and may include the same MEMS devices or different MEMS devices. For example, the first MEMS device 1136 may be an accelerometer and the second MEMS device 1138 may be a gyroscope. In various embodiments, the first cavity 1132 and the second cavity 1134 are sealed, for example, by the eutectic bonds. As a result of the sealing, the first MEMS device 1136 may include a first gas pressure and the second MEMS device 1138 may include a second gas pressure. In various embodiments, the first gas pressure and the second gas pressure may be different or the same, and one or both of the pressures may be a vacuum.
As described above, the first bump stops 914 include a single layer (e.g. the first conductive layer 608) with a first height. In addition, the second bump stops 916 include a double layer (e.g. the first conductive layer 608 and the second conductive layer 610) with a second height that is larger than the first height. Furthermore, the first bump stops 914 and the second bump stops 916 may include any number of layers, and the number of layers may be different or equal. In various embodiments, the first bump stops 914 and the second bump stops 916 may perform any number of similar or different functions. For example, one or more of the first bump stops 914 and the second bump stops 916 may function as sensing electrodes, shield electrodes, etc.
In further embodiments, the first cavity 1132 of the first MEMS device 1136 may include one or more of the first bump stops 914 as well as one or more of the second bump stops 916. In addition, the second cavity 1134 of the second MEMS device 1138 may include one or more of the first bump stops 914 as well as one or more of the second bump stops 916. Therefore, it is understood that by using the masking and etching described herein, any combination of first bump stops 914 and second bump stops 916 may be formed within one or more cavities associated with one or more MEMS devices.
While the embodiments have been described and/or illustrated by means of particular examples, and while these embodiments and/or examples have been described in considerable detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the embodiments to such detail. Additional adaptations and/or modifications of the embodiments may readily appear, and, in its broader aspects, the embodiments may encompass these adaptations and/or modifications. Accordingly, departures may be made from the foregoing embodiments and/or examples without departing from the scope of the concepts described herein. The implementations described above and other implementations are within the scope of the following claims.
Claims
1. A method comprising:
- forming a micro-electro-mechanical system (“MEMS”) wafer including a first MEMS device and a second MEMS device;
- forming a complementary metal-oxide semiconductor (“CMOS”) wafer including a first electrically conductive via and a second electrically conductive via;
- depositing a layer stack including a first conductive layer, a second conductive layer, and a bond layer over the first electrically conductive via and the second electrically conductive via;
- etching the layer stack to define a first standoff, a second standoff, a third standoff, a first bump stop over the first electrically conductive via, and a second bump stop over the second electrically conductive via;
- etching the first bump stop and the second bump stop to remove the bond layer;
- further etching the first bump stop to remove the second conductive layer; and
- bonding the MEMS wafer to the CMOS wafer.
2. The method of claim 1, further comprising depositing a photoresist over the first standoff, the second standoff, and the third standoff, prior to the etching the first bump stop and the second bump stop.
3. The method of claim 1, further comprising depositing a photoresist over the second bump stop, prior to the further etching the first bump stop.
4. The method of claim 1, wherein the bonding the MEMS wafer to the CMOS wafer includes eutecticly bonding the first standoff, the second standoff, and the third standoff to the MEMS wafer.
5. The method of claim 1, wherein the eutecticly bonding the MEMS wafer to the CMOS wafer forms
- a first cavity surrounding the first MEMS device and the first bump stop, and
- a second cavity surrounding the second MEMS device and the second bump stop.
6. The method of claim 5, wherein the first cavity includes a first gas pressure and the second cavity includes a second gas pressure.
7. The method of claim 1, wherein
- the first MEMS device is between the first standoff and the second standoff, and
- the second MEMS device is between the second standoff and the third standoff.
8. A method comprising:
- depositing a layer stack on a complementary metal-oxide semiconductor (“CMOS”) wafer, wherein the layer stack includes a first conductive layer and a second conductive layer over a first electrically conductive via and a second electrically conductive via;
- etching the layer stack to remove the second conductive layer over the first electrically conductive via to expose a portion of the first conductive layer over the first electrically conductive via;
- depositing a bond layer over the second conductive layer and the exposed portion of the first conductive layer;
- etching the bond layer, the first conductive layer, and the second conductive layer to form a first standoff, a second standoff, and a third standoff, wherein the first standoff, the second standoff and the third standoff include portions of the first conductive layer, the second conductive layer, and the bond layer, a first bump stop over the first electrically conductive via, wherein the first bump stop includes portions of the first conductive layer and the bond layer, and a second bump stop over the second electrically conductive via, wherein the second bump stop includes portions of the first conductive layer, the second conductive layer, and the bond layer;
- removing the bond layer from the first bump stop and the second bump stop; and
- bonding a MEMS wafer to the CMOS wafer.
9. The method of claim 8, further comprising depositing a photoresist over the first standoff, the second standoff, and the third standoff, prior to the removing the bond layer from the first bump stop and the second bump stop.
10. The method of claim 8, wherein the removing the bond layer from the first bump stop and the second bump stop includes etching the bond layer.
11. The method of claim 8, wherein the bonding the MEMS wafer to the CMOS wafer includes eutecticly bonding the first standoff, the second standoff, and the third standoff to the MEMS wafer.
12. The method of claim 8, wherein the eutecticly bonding the MEMS wafer to the CMOS wafer forms
- a first cavity surrounding a first MEMS device and the first bump stop, and
- a second cavity surrounding a second MEMS device and the second bump stop.
13. The method of claim 12, wherein the first cavity includes a first gas pressure and the second cavity includes a second gas pressure.
14. The method of claim 8, wherein
- a first MEMS device is between the first standoff and the second standoff, and
- a second MEMS device is between the second standoff and the third standoff.
15. An apparatus comprising:
- a micro-electro-mechanical system (“MEMS”) wafer including a first MEMS device and a second MEMS device;
- a complementary metal-oxide semiconductor (“CMOS”) wafer underlying the MEMS wafer, wherein the CMOS wafer and the MEMS wafer are bonded together;
- a first sealed cavity surrounding the first MEMS device, wherein the first sealed cavity is defined by the MEMS wafer and the CMOS wafer;
- a second sealed cavity surrounding the second MEMS device, wherein the second sealed cavity is defined by the MEMS wafer and the CMOS wafer;
- a first conductive bump stop on the CMOS wafer and in the first sealed cavity, wherein the first conductive bump stop includes a first height; and
- a second conductive bump stop on the CMOS wafer and in the second sealed cavity, wherein the second conductive bump stop includes a second height.
16. The apparatus of claim 15, wherein the first conductive bump stop includes one conductive layer and the second conductive bump stop includes two conductive layers.
17. The apparatus of claim 15, wherein the second height is larger than the first height.
18. The apparatus of claim 15, wherein
- the first MEMS device is an accelerometer and the second MEMS device is a gyroscope, or
- the first MEMS device is a gyroscope and the second MEMS device is an accelerometer.
19. The apparatus of claim 15, wherein a first gas pressure in the first sealed cavity is different than a second gas pressure in the second sealed cavity.
20. The apparatus of claim 15, wherein
- the first MEMS device and the first conductive bump stop are between a first standoff and a second standoff, and
- the second MEMS device and the second conductive bump stop are between a second standoff and a third standoff.
Type: Application
Filed: Jul 10, 2017
Publication Date: Jan 18, 2018
Patent Grant number: 10081539
Inventors: Daesung LEE (San Jose, CA), Jeff HUANG (Fremont, CA), Ki Young LEE (Milpitas, CA)
Application Number: 15/645,665